In a pre-stressed concrete structure such as a concrete wall or a concrete beam a steel strand is tensioned and concrete is poured directly around the strand for curing, allowing bonding of the concrete with the strand.
Once cured, the steel strand tension is released resulting in compression of the concrete structure. The bond strength of the strand to concrete keeps the compression intact.
The prior art knows such pre-stressed concrete structures with uncoated steel strands.
Concrete is an alkaline environment and in quite some applications, there is no problem with the life time and corrosion of the reinforcing steel strands. However, in other more demanding applications, e.g. in marine environments, there is a huge demand to increase the life time of pre-stressed concrete structures, and, as a consequence the life time of the reinforcing steel strands.
Using galvanized steel strands did not result in reaching the same bond strengths as with uncoated steel strands, on the contrary, the bond strength of galvanized steel strands to cement or concrete was lower than with uncoated steel strands.